This application addresses broad Challenge Area 06: Enabling Technologies. The specific Challenge Topic is 06-NS-103: Breakthrough Technologies in Neuroscience. Virtual reality (VR) is a technology that allows a user to interact with a computer- simulated environment. The environment can represent a simulation of the real world or an imaginary world that can be modified in real time to provide a novel probe of cognition. Widely used in human behavior and neuro-imaging experiments, we now propose to bring this technology to bear on diverse areas in the study of neural circuits at cellular resolution in rodents. We will develop VR instrumentation and software that can work in a synergistic way with both in vivo two photon laser scanning microscopy and in vivo whole cell patch recording to provide new capabilities in systems neuroscience. The technology revolves around the use of head-restrained rodents walking and running on the surface of a levitated sphere. We have recently demonstrated that this spherical treadmill can be used with two-photon laser scanning microscopy to provide measurements of calcium transients at cellular resolution from populations (~100) of cortical neurons in awake, mobile, mice. To add visual VR capability, a toroidal screen that spans the rodent visual field surrounds the ball. This screen displays a projected computer generated image that has been geometrically transformed to provide a realistic image of the virtual environment from the mouse's perspective. Sensors that detect the motion of the ball produced by movements of the subject provide a control signal to a computer for both turning and forward motion within the environment. Recently completed pilot experiments using this apparatus demonstrate that mice, in an instrumental conditioning paradigm, learn to navigate in virtual arenas and mazes for water rewards. Single unit recordings demonstrate place cells in the virtual environments. Furthermore, the system provides the capability to apply in vivo whole cell intracellular recording methods during navigation and the first intracellular recordings of place cells are demonstrated. By combining VR with two-photon imaging, the capability for monitoring populations of hippocampal pyramidal cells during navigation is also demonstrated. Based on these results, a team of investigators working in diverse areas of neuroscience will work together to expand the development of VR systems for rodents as a new breakthrough technology. First, we will develop improved displays, spherical treadmills, motion sensors, and visual VR software based on experience with the first generation system. This will improve the performance of the existing visual VR system in general and also allow it to be easily adopted by the wider neuroscience community. VR environments for the characterization of place cells and grid cells will be constructed and the characteristics of these cells will be compared to that observed in real environments. Second, we will develop a spherical treadmill and associated instrumentation for head restrained rat VR, a species widely used in studies of navigation and, more recently, executive control. Third, we will develop instrumentation for adding new sensory modalities and feedback capabilities. VR-controlled olfactory and auditory stimuli will be developed. For studies of the role of the cerebellum in motor control, a computer-controlled resistance treadmill will be developed that provides proprioceptive feedback in real-time. In all cases, the VR instrumentation will be optimized for use with in vivo two-photon laser scanning microscopy and whole cell intracellular patch recording. When completed, the suite of new instrumentation will provide the systems neuroscience community with new capabilities for cellular analysis of circuits in awake behaving rodents. This study will develop virtual reality systems for use in neuroscience research. The system will enable the measure of electrical and chemical processes in one or many individual neurons in the brain while the subject is navigating in a virtual environment. This capability would be valuable in comparing normal and diseased states in the brain. The methods developed will be applicable to the mouse, which is the leading mammalian genetic model in health research. It will also be developed for the rat, a species widely used in behavioral studies.